In the 26th century, the Doctor, Adric, Nyssa and Tegan come to the aid
of a platoon of soldiers, which is investigating the murder of a
scientific team in a cave complex on Earth. The Doctor discovers that
the killers are actually androids serving the Cybermen, and are guarding
a bomb intended to destroy the planet. The Doctor disarms the explosive
but by tracing the detonation signal, he learns that the greatest danger
is yet to come. The Cybermen have secreted themselves on board a
freighter heading for Earth, which will unknowingly serve as the
bridgehead for a massive invasion.

Production

The story originally scheduled to be the penultimate adventure of
Doctor Who's nineteenth season was “The Enemy Within”
by well-regarded science-fiction author Christopher Priest. A storyline
for this serial was commissioned by script editor Christopher H Bidmead
on December 5th, 1980. Shortly thereafter, Bidmead left Doctor
Who and was replaced on an interim basis by Antony Root, who
requested full scripts for “The Enemy Within” on February
6th, 1981.

Around this time, producer John Nathan-Turner decided to write Adric out
of Doctor Who: the character was now viewed as unsuccessful, and
actor Matthew Waterhouse had been a sometimes awkward presence on set.
Nathan-Turner felt that Adric did not lend himself to a traditional
departure scenario, however, and instead decided that he should be
killed off. Not only would this accrue a lot of publicity for Doctor
Who -- no regular character had exited the programme in that manner
since short-lived companions Katarina and Sara Kingdom in Season Three's
The Daleks' Master Plan -- but Nathan-Turner
also thought that it would imbue Doctor Who with a greater sense
of danger and excitement, while making the surviving characters much
less invulnerable than had previously been the case.

John Nathan-Turner felt that Adric did not lend himself to
a traditional departure, and should be killed off

It was decided that “The Enemy Within” should be the story
in which Adric met his end; Priest duly amended his plot and completed
his scripts. In mid-June, however, a serious disagreement arose between
Priest and Nathan-Turner over payments for rewrites. Following a
venomous telephone conversation, it became clear that “The Enemy
Within” would have the be withdrawn from the schedule and replaced
with a new story.

By now, Root's three-month tenure on Doctor Who had come to an
end, and he had been replaced as script editor by another trainee named
Eric Saward. It had originally been anticipated that Saward would merely
fill the gap before Root could come back to Doctor Who, but by
June it had become clear that Root would not be returning. Instead, the
decision was made to install Saward as the programme's permanent script
editor. Under BBC regulations, this meant that Saward was now forbidden
from writing new Doctor Who serials, but he and Nathan-Turner
nonetheless agreed that he would provide the replacement for “The
Enemy Within”. This was made possible by the expiry of Saward's
initial three-month contract towards the end of June; consequently,
permission was sought for Saward to write a story called
“Sentinel” on June 29th, just before his new long-term
contract came into effect. To further avoid any appearance of
impropriety, Root agreed to perform minor work on “Sentinel”
so that he could be credited as the script editor.

Both Saward and Peter Davison were fans of the Cybermen, a monster which
had featured in Doctor Who only once since 1968 (in 1975's
Revenge Of The Cybermen). Urged on by fan
advisor Ian Levine, Nathan-Turner was eager to bring back popular
monsters from the series' past, and readily agreed to the return of the
Cybermen in “Sentinel”. Tired of Doctor Who monsters
always being killed off at the end of the first appearance, Saward
considered having the Cyber Leader survive “Sentinel” --
providing yet another sign of the Fifth Doctor's fallibility in
comparison to his predecessor -- but ultimately decided against it.
Meanwhile, it fell to Nathan-Turner to inform Waterhouse of his
character's fate. The young actor was initially appalled by the
decision, because Adric's death meant that he would not be able to
return to Doctor Who at a later date. He was mollified to an
extent, however, when the producer pointed out that the Doctor could
always encounter Adric at a time prior to his demise.

Dinah Collin decided that the new Cybermen should wear
army G-suits instead of rubber diving suits

Costume designer Dinah Collin was assigned the task of bringing the
Cybermen into the Eighties, and worked on the project with Richard
Gregory of effects firm Imagineering. They decided to abandon the rubber
diving suits which had previously been the basis of the Cyberman outfit,
opting instead of the more high-tech look of army G-suits. At
Nathan-Turner's suggestion, the jaws of the updated Cybermen were left
clear so that the actors' mouths could be seen; the producer felt that
this would reinforce the notion that the Cybermen had once been human.
In a similar vein, Collin and Gregory considered leaving the Cybermen's
hands bare -- as had been the case in their first appearance, in 1966's
The Tenth Planet -- and then seamlessly
integrating the flesh with the Cyberman's “metallic” arm.
However, it was ultimately decided that this effect would be too complex
to achieve. Collin also wanted to do away with the
“handlebars” on the sides of the Cyberman helmets, but this
was vetoed by Nathan-Turner and Saward, who felt that they were an
essential part of the Cyberman image.

During October, “Sentinel” -- designated Serial 6B -- was
retitled Earthshock. Its director was Peter Grimwade, who had
just completed Kinda. Grimwade, Saward and
Nathan-Turner were all keen that Earthshock should try, as much
as possible, to capture the fast-paced feel of a feature film. As a
result, Grimwade's final camera scripts were extremely lengthy, with
part four alone running to eighty-nine scenes: far more than was normal
for Doctor Who at that time.

Work on Earthshock began on October 29th with location filming at
Springwell Lock Quarry in Rickmansworth, Hertfordshire, for the
exteriors of the cave complex. Studio recording then comprised two
three-day sessions in BBC Television Centre Studio 8. The first of these
took place from November 10th to 12th. The opening day dealt with most
of the TARDIS interior scenes. Material in the main cavern and the
various tunnels was the focus on the 11th, together with some of the
sequences in the small cavern. These were completed on the 12th, along
with the awakening of the dormant Cybermen and the climactic TARDIS
scenes.

Also recorded on November 12th was all of the action in Cyber Control,
which included flashbacks to older Doctor Who stories.
Nathan-Turner had been delighted by the reception of a similar sequence
in the concluding episode of Logopolis the
previous year, and so was keen to include more such moments in Season
Nineteen. Earthshock was an obvious candidate, and Saward and
Levine worked together to select one clip for each Doctor who had
previously encountered the Cybermen. They settled on extracts from The Tenth Planet (the First Doctor), The Wheel In Space (the Second Doctor) and Revenge Of The Cybermen (the Fourth Doctor).
The latter segment was converted to monochrome to preserve continuity
with the first two clips.

The idea of running silent end credits for episode four
was borrowed from Coronation Street

The second studio block spanned November 24th to 26th, and included all
of the scenes set aboard the freighter. Although Adric's death was
amongst the material filmed, Waterhouse's time on Doctor Who was
not yet over, as the actor was required to appear as an ersatz Adric in
the season's concluding serial, Time-Flight. Model shots were also taped on
the final day; the freighter mock-up included elements which were an
intentional homage to the Nostromo from the 1979 feature film
Alien. By this stage, it had been decided that Earthshock
part four would conclude with the credits running silently over a shot
of Adric's shattered badge for mathematical excellence; Nathan-Turner
had borrowed this idea from a broadcast of the long-running soap opera
Coronation Street. This would mark the only occasion in the
programme's history in which a Doctor Who episode would not end
with the traditional theme tune.

In post-production, Grimwade became very unhappy with the incidental
music composed by Malcolm Clarke, which largely relied on natural
metallic sounds such as hammers striking girders. The director
complained to Nathan-Turner about the score, but because no time
remained for a replacement to be created, it was decided to retain
Clarke's composition. Meanwhile, the BBC's listings magazine Radio
Times offered Nathan-Turner a cover to promote the return of the
Cybermen. The producer was keen to keep the monsters (and Adric's fate)
a secret, however, and declined the invitation, despite the fact that
Doctor Who had not appeared on a Radio Times cover since
1973.

The broadcast of Earthshock episode four brought Antony Root's
connection with Doctor Who to a belated close. Root went on to
script edit The Chinese Detective before leaving the BBC. He
subsequently became a producer, earning credits on programmes such as
Cold Comfort Farm, The Grand, and the American remake of
Touching Evil, as well as the 1991 movie Edward II. Root
also served as Head of Drama at Thames Television.